The Biotechnology Resource in electron probe microanalysis uses new and complex microanalytical methods to study the elemental composition of biological tissues through Core Research and Development, and Collaborative Research with the biological community at Harvard and other institutions in the nation. The primary instrument, an electron probe microanalyzer, is capable of localizing and quantitating any chemical element heavier than boron within a submicron volume (10 to the minus 15th power or less), hence within single cells, in quantities less than 10 to the minus 16th power. The best use of this unique analytical tool in biology is dependent upon the development of methods of sample preparation. The Resource has developed and routinely performs complete elemental analysis on liquid samples 10 to the minus 11th power liters, or on large populations of individual isolated cells. A mini-computer is used for an "on-line" control of the instrument and for useful data manipulation. The Resource will put a major emphasis on the analysis of diffusible elements in biological tissues either in 10 to the minus 15th power volumes of cells r extracellular fluid in bulk samples kept frozen-hydrated, or in 10 to the minus 18th power volumes between cells or in intracellular organelles or pools in thin or ultra thin freeze-dried or frozen-hydrated sections. Ultrastructural localization of molecules will be developed. Exploration of new microanalytical methods (proton probe, ion probe) will continue. Original results have been and should continue to be obtained in cell, renal, reproductive, digestive, endocrine, auditory and vision biology.